1. Technical Field
The present invention relates to a power control device and method for a universal serial bus (USB) in a computer system, and more particularly to a power control device and method for controlling power supplied to a universal serial bus which is connected to a display and a computer system. More specifically, the present invention relates to a power control device and method for controlling the source of power supplied to a universal serial bus where, under normal operating conditions, power is supplied from a display device to a universal serial bus, and, when there is a failure or abnormality in the power supplied from the display device to the universal serial bus, power is supplied from a computer to the universal serial bus.
2. Related Art
A typical personal computer has peripheral devices connected, such as a monitor and keyboard. A user might want to use additional peripheral devices, such as a mouse, printer, light pen, or plotter. When a user tries to use multiple peripheral devices with a computer, it can be difficult to connect them since each peripheral typically has a unique type of connector. The user must carefully match the plug from each peripheral with a corresponding connector on the computer due to all the different connector types. Also, it can be difficult to configure the computer to communicate with all the peripheral devices due to the fact that some peripheral devices require unique types of hardware and software. The task of adding peripheral devices to a computer can be especially arduous for computers that do not support plug-and-play.
To solve the above described problems, a universal serial bus (USB) system has been developed. The universal serial bus is a basic system for connecting peripheral devices to a computer. Peripheral devices connected to a universal serial bus system are also referred to as universal serial bus peripheral devices.
A keyboard or monitor can be directly connected to a computer or a universal serial bus within the computer. Other peripheral devices can be easily connected to the computer with the use of an expanded hub built into the keyboard or monitor, or even via an independent universal serial bus. The expanded hub offers additional connection sockets, and can be connected in a hierarchical tree form. Peripheral devices may be located close to each other or can be located several meters from each other, with the use of a universal serial bus hub.
A universal serial bus is able to connect a total of 127 devices to one computer. The operating voltage transmitted through the universal serial bus is limited to 5 volts. Thus, peripherals connected on a universal serial bus are limited in the amount of power they can consume. A rapid data transmission rate of 12 megabits per second on the universal serial bus is one of the advantageous features of the universal serial bus.
The major advantages of the universal serial bus include the simplicity and convenience of attaching and detaching peripheral devices to the computer. The universal serial bus detects whether a device is added or removed when related information is offered from a computer. This operation is available while the power is ON, unlike existing built-in slots, eliminating the system reboot.
Some examples of universal serial bus systems are disclosed in U.S. Pat. No. 5,621,901 for Method and Apparatus for Serial Bus Elements of an Hierarchical Serial Bus Assembly to Electrically Represent Data and Control States to Each Other issued to Morriss et al., U.S. Pat. No. 5,623,610 for System for Assigning Geographical Addresses in a Hierarchical Serial Bus byEnabling Upstream Port and Selectively Enabling Disabled Ports at Power On/Reset issued to Knoll et al., and U.S. Pat. No. 5,675,813 for System and Method for Power Control in a Universal Serial Bus issued to Holmdahl.
Some examples of power control devices and methods are disclosed in U.S. Pat. No. 5,559,376 for Power Supply Control System Comprising a Plurality of Power Supply Units issued to Tachikawa, U.S. Pat. No. 5,486,726 for Power Supply Control System of Peripheral Equipment of Computer issued to Kim et al, U.S. Pat. No. 5,404,542 for Power Line Switching Circuit with Monitor issued to Cheung, U.S. Pat. No. 5,163,124 for Method and Apparatus for Controlling Power to Device in a Computer System issued to Yabe et al., U.S. Pat. No. 5,596,757 for System and Method for Selectively Providing Termination Power to a SCSI Bus Terminator from a Host Device issued to Smith, U.S. Pat. No. 5,550,985 for Special Purpose Computer for Demonstrating Peripheral Devices such as Printers in Which Power is Withdrawn from the Port Connection of the Peripheral Device issued to Miller et al., and U.S. Pat. No. 5,664,089 for Multiple Power Domain Power Loss Detection and Interface Disable issued to Byers et al.
Although presently there do exist systems which partially control the power supplied to a universal serial bus, I have discovered that it would be desirable to further enhance the power control of a universal serial bus to enable it to have a secondary source of power in the event that a primary source of power fails.